How to fix error message to edit sidebar widget text on a livesite childtheme?

Question

My WordPress livesite says "An error has occurred. Please reload the page and try again" when I try to edit the sidebar widget text of a twentysixteen child theme. I copied the website to localhost and I did not receive the same error message (I could edit the text just fine). The error occurs with the livesite child theme even with only a "functions.php" file and a "style.css" file. I tried disabling all plugins but I received the same error.

The picture below shows me attempting to change the "Directories" name causing error.

Answer 1

I fixed the issue. From error_log in public_html/wp-admin I found:

I looked some to see whether it was specific to my livesite, something like indexing, but the error was that I closed my functions.php with a "?>" and there may have been whitespace afterwards that was attempted to be sent which caused conflict. I erased the ending "?>" in functions.php for my child theme and I no longer get the error. I'm not currently completely sure why when I duplicated the livesite to localhost of why I did not receive an error in editing the localsite the same way but it's possible that the whitespace was removed.